Semiconductor lasers emit radiation with spatial and temporal coherence. Radiation from semiconductor lasers is highly monochromatic and produces highly directional beams of light. Semiconductor lasers are generally very compact in size, and are efficient. Radiation is formed in a semiconductor laser within the active region of the laser and emitted vertically with respect to the laser surface.
Vertical cavity surface emitting lasers (VCSELs) are a type of semiconductor lasers that have a very low threshold current, a high beam quality, and high speed operation. VCSELs are formed by placing the active region between two highly reflective mirrors, called Bragg mirrors, formed from alternating layers of semiconductor materials with high and low indices of refraction. The configuration of the active region and the Bragg mirrors allows for a standing wave to be formed between the lower and upper mirrors, which increase the efficiency of the VCSEL.
Semiconductor lasers, especially VCSELs are used in numerous applications where efficient sources of radiation are desired. VCSELs are often configured with different types of photodetectors and optical systems for use in various applications, such as for example, object detection, velocity measurement, and length measurement.
Systems for accomplishing such tasks as object detection, velocity measurement, and length measurement can often require very expensive components, including optical systems, and multiple lasers. Such systems are also often quite large, and generally require the system to be configured very specifically with the object to be detected in order to maintain alignment for proper detection. Examples of some such devices include those disclosed in U.S. Pat. No. 5,513,201, Yamaguchi et al., discloses a device that includes a linear array laser diode and an optical path rotating device designed to convert the dotted line output of the linear array laser diode into an output that has a structure similar to ladder rungs for rotating the optical path of a laser. Further, U.S. Pat. No. 5,644,413, Komma et al., discloses a device that includes a semiconductor laser, an elaborate lens system, and a photodetector designed to shift the relative position of the information medium and the optical head in a magnetic read/write system.
U.S. Pat. No. 5,805,748, Izawa, discloses a system that includes a laser beam divided into a number of beam sections along the horizontal direction, and a beam converging guide that focuses the laser beam into a more circular cross section. U.S. Pat. No. 6,014,360 discloses a system that includes a laser beam, and an optical intensity converting means, which is generally an objective lens, that functions to condense the laser beam to create a smaller beam for use in optical recording heads.
U.S. Pat. No. 5,504,345, Bartunek et al., discloses a system for detecting the edge of an object that includes two light sources positioned so that the respective beams are focused at the same point on the object, and two detectors which monitor the reflected light from the object. U.S. Pat. No. 6,130,437, Cerney et al., discloses an improvement to the above edge detection system that includes a transmitter, associated optical elements, and a receiver for detecting the edge of an object. This system provides a wider angle of detection than Bartunek does.
Although systems such as these can accomplish the required tasks, they can be expensive and often must be exactingly aligned. As a result, there remains a need for low cost, compact, reliable systems that are capable of accomplishing tasks such as object detection, velocity measurement, and length measurement.